Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

CastCheck methodology v0.2 · data through 2026-08-30

Philadelphia Intl · NCEP GFS · lead day 9

KPHL · gfs · lead 9

Target day = initialization date + 9 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, gfs-0p25, starting 2026-08-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d21 1 QC5.14 [3.89, 6.26]5.19-1.32 [-3.94, 1.53]6.42 [5.17, 7.25]14% [0%, 29%]33%43%-0.29-0.722026-08-10 → 2026-08-30
tmax00Zbilinear90d21 1 QC5.14 [3.69, 6.22]5.19-1.32 [-4.02, 2.00]6.42 [4.70, 7.26]14% [0%, 29%]33%43%-0.29-0.722026-08-10 → 2026-08-30
tmax00Zbilinear365d21 1 QC5.14 [3.77, 6.24]5.19-1.32 [-4.30, 2.05]6.42 [4.66, 7.25]14% [0%, 29%]33%43%-0.29-0.722026-08-10 → 2026-08-30
tmax00Zbilinearall21 1 QC5.14 [3.94, 6.24]5.19-1.32 [-4.57, 2.08]6.42 [4.84, 7.26]14% [0%, 29%]33%43%-0.29-0.722026-08-10 → 2026-08-30
tmax00Znearest30d21 1 QC5.18 [3.87, 6.39]5.26-1.53 [-4.25, 1.31]6.53 [5.21, 7.41]19% [0%, 39%]43%43%-0.29-0.752026-08-10 → 2026-08-30
tmax00Znearest90d21 1 QC5.18 [3.67, 6.35]5.26-1.53 [-4.41, 1.95]6.53 [4.79, 7.45]19% [0%, 41%]43%43%-0.29-0.752026-08-10 → 2026-08-30
tmax00Znearest365d21 1 QC5.18 [3.71, 6.36]5.26-1.53 [-4.65, 1.99]6.53 [4.83, 7.44]19% [0%, 43%]43%43%-0.29-0.752026-08-10 → 2026-08-30
tmax00Znearestall21 1 QC5.18 [3.84, 6.40]5.26-1.53 [-4.91, 2.00]6.53 [4.95, 7.44]19% [0%, 43%]43%43%-0.29-0.752026-08-10 → 2026-08-30
tmax12Zbilinear30d21 1 QC5.98 [4.56, 7.14]5.85-1.50 [-4.60, 2.15]7.63 [5.76, 9.08]14% [6%, 27%]24%33%-0.50-0.942026-08-10 → 2026-08-30
tmax12Zbilinear90d21 1 QC5.98 [4.40, 7.16]5.85-1.50 [-4.66, 2.61]7.63 [5.23, 9.05]14% [0%, 27%]24%33%-0.50-0.942026-08-10 → 2026-08-30
tmax12Zbilinear365d21 1 QC5.98 [4.27, 7.21]5.85-1.50 [-4.62, 2.96]7.63 [4.93, 9.09]14% [0%, 26%]24%33%-0.50-0.942026-08-10 → 2026-08-30
tmax12Zbilinearall21 1 QC5.98 [4.11, 7.10]5.85-1.50 [-4.66, 3.20]7.63 [4.86, 9.05]14% [5%, 32%]24%33%-0.50-0.942026-08-10 → 2026-08-30
tmax12Znearest30d21 1 QC6.25 [4.73, 7.41]6.00-1.62 [-4.83, 2.21]7.94 [5.98, 9.49]10% [0%, 25%]19%33%-0.56-0.992026-08-10 → 2026-08-30
tmax12Znearest90d21 1 QC6.25 [4.16, 7.45]6.00-1.62 [-4.99, 2.67]7.94 [5.39, 9.49]10% [0%, 27%]19%33%-0.56-0.992026-08-10 → 2026-08-30
tmax12Znearest365d21 1 QC6.25 [4.19, 7.52]6.00-1.62 [-4.93, 2.95]7.94 [4.94, 9.60]10% [0%, 25%]19%33%-0.56-0.992026-08-10 → 2026-08-30
tmax12Znearestall21 1 QC6.25 [4.01, 7.47]6.00-1.62 [-4.93, 3.30]7.94 [4.85, 9.51]10% [0%, 30%]19%33%-0.56-0.992026-08-10 → 2026-08-30
tmin00Zbilinear30d21 1 QC4.19 [2.83, 5.00]4.21-0.06 [-2.87, 2.97]5.16 [3.98, 5.79]10% [0%, 22%]33%52%+0.08-0.212026-08-10 → 2026-08-30
tmin00Zbilinear90d21 1 QC4.19 [2.41, 5.04]4.21-0.06 [-2.97, 3.09]5.16 [3.54, 5.75]10% [0%, 25%]33%52%+0.08-0.212026-08-10 → 2026-08-30
tmin00Zbilinear365d21 1 QC4.19 [2.43, 5.10]4.21-0.06 [-3.16, 3.53]5.16 [3.55, 5.82]10% [0%, 25%]33%52%+0.08-0.212026-08-10 → 2026-08-30
tmin00Zbilinearall21 1 QC4.19 [2.22, 5.15]4.21-0.06 [-3.12, 3.82]5.16 [3.11, 5.80]10% [0%, 26%]33%52%+0.08-0.212026-08-10 → 2026-08-30
tmin00Znearest30d21 1 QC4.04 [2.81, 4.84]4.11-0.98 [-3.67, 1.92]5.20 [3.88, 5.98]24% [14%, 41%]38%52%+0.12-0.182026-08-10 → 2026-08-30
tmin00Znearest90d21 1 QC4.04 [2.50, 4.78]4.11-0.98 [-3.85, 2.06]5.20 [3.59, 5.94]24% [14%, 44%]38%52%+0.12-0.182026-08-10 → 2026-08-30
tmin00Znearest365d21 1 QC4.04 [2.59, 4.93]4.11-0.98 [-3.97, 2.44]5.20 [3.68, 6.10]24% [14%, 44%]38%52%+0.12-0.182026-08-10 → 2026-08-30
tmin00Znearestall21 1 QC4.04 [2.38, 4.90]4.11-0.98 [-3.87, 2.84]5.20 [3.32, 6.08]24% [14%, 48%]38%52%+0.12-0.182026-08-10 → 2026-08-30
tmin12Zbilinear30d21 1 QC4.27 [3.09, 5.15]4.27+0.06 [-2.88, 2.79]4.80 [3.82, 5.55]14% [0%, 38%]14%24%+0.07-0.232026-08-10 → 2026-08-30
tmin12Zbilinear90d21 1 QC4.27 [2.74, 5.13]4.27+0.06 [-2.96, 3.05]4.80 [3.48, 5.58]14% [0%, 46%]14%24%+0.07-0.232026-08-10 → 2026-08-30
tmin12Zbilinear365d21 1 QC4.27 [2.99, 5.29]4.27+0.06 [-3.15, 3.12]4.80 [3.69, 5.70]14% [0%, 42%]14%24%+0.07-0.232026-08-10 → 2026-08-30
tmin12Zbilinearall21 1 QC4.27 [3.04, 5.32]4.27+0.06 [-3.12, 3.38]4.80 [3.71, 5.70]14% [0%, 40%]14%24%+0.07-0.232026-08-10 → 2026-08-30
tmin12Znearest30d21 1 QC4.17 [2.80, 5.28]4.10-0.75 [-3.61, 1.95]4.76 [3.36, 5.68]10% [0%, 21%]24%29%+0.09-0.182026-08-10 → 2026-08-30
tmin12Znearest90d21 1 QC4.17 [2.43, 5.36]4.10-0.75 [-3.65, 2.19]4.76 [3.01, 5.75]10% [0%, 24%]24%29%+0.09-0.182026-08-10 → 2026-08-30
tmin12Znearest365d21 1 QC4.17 [2.63, 5.50]4.10-0.75 [-3.82, 2.25]4.76 [3.20, 5.95]10% [0%, 22%]24%29%+0.09-0.182026-08-10 → 2026-08-30
tmin12Znearestall21 1 QC4.17 [2.65, 5.36]4.10-0.75 [-3.74, 2.53]4.76 [3.21, 5.81]10% [0%, 22%]24%29%+0.09-0.182026-08-10 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for NCEP GFS at KPHL, lead day 9, 00Z bilinear tmax+20+100-10-202026-08-10: +2.41 °F2026-08-11: +6.08 °F2026-08-12: +4.98 °F2026-08-13: -11.36 °F2026-08-14: -9.5 °F2026-08-15: -3.12 °F2026-08-16: -1.19 °F2026-08-17: -9.67 °F2026-08-18: -0.26 °F2026-08-19: -6.54 °F2026-08-20: +0.03 °F2026-08-21: -2.75 °F2026-08-22: +9.58 °F2026-08-23: +1.97 °F2026-08-24: +0.46 °F2026-08-25: +11.25 °F2026-08-26: -7.48 °F2026-08-27: +1.52 °F2026-08-28: -10.56 °F2026-08-29: +1.88 °F2026-08-30: -5.43 °F2026-08-102026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-5.43
2026-08-29+1.88
2026-08-28-10.56
2026-08-27+1.52
2026-08-26-7.48
2026-08-25+11.25
2026-08-24+0.46
2026-08-23+1.97
2026-08-22+9.58
2026-08-21-2.75
2026-08-20+0.03
2026-08-19-6.54
2026-08-18-0.26
2026-08-17-9.67
2026-08-16-1.19
2026-08-15-3.12
2026-08-14-9.50
2026-08-13-11.36
2026-08-12+4.98
2026-08-11+6.08
2026-08-10+2.41

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 9-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 0 days-12 to -10 °F: 2 days-10 to -8 °F: 2 days-8 to -6 °F: 2 days-6 to -4 °F: 1 day-4 to -2 °F: 2 days-2 to 0 °F: 2 days0 to 2 °F: 5 days2 to 4 °F: 1 day4 to 6 °F: 1 day6 to 8 °F: 1 day8 to 10 °F: 1 day10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 4.98 · P90 |e| 10.56 °F-200+20 °Fn = 21 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-20.00-18.000
-18.00-16.000
-16.00-14.000
-14.00-12.000
-12.00-10.002
-10.00-8.002
-8.00-6.002
-6.00-4.001
-4.00-2.002
-2.00+0.002
+0.00+2.005
+2.00+4.001
+4.00+6.001
+6.00+8.001
+8.00+10.001
+10.00+12.001
+12.00+14.000
+14.00+16.000
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08215.14 -1.32

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means NCEP GFS has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 21 +0.19 [-1.49, 1.95] no
GraphCast (IFS init) 21 -0.72 [-2.71, 1.09] no
ECMWF IFS HRES 16 -0.62 [-6.09, 2.76] no
Persistence (baseline) 21 +1.14 [-0.95, 3.42] no

Cite this page

ShortCastCheck, KPHL gfs lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), model gfs, lead day 9. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/9/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence